You can't fix it with an addon, shadow dance has no interaction with the WoW API, it's literally impossible to recreate its functionality in anyway. Trust me I've tried writing the addon a few different ways.

We do recognize that there is contention around the change we made to Shadow Dance with it no longer using the stealth bar and that it's no longer a macro conditional.

Simply put, we don’t want macros or UI mods to conditionally merge abilities for you (ie, we don’t want you to be able to merge Fireball and Pyroblast in a macro, etc). This is similar to how we no longer allow you to merge Backstab and Shadowstrike. There’s a couple of goals here, but the main one is that these abilities should all feel like they have very firm distinctions from each other, and it’s okay for you to have to press an extra button in order to achieve that.

Subtlety has been a bit of a stand-out in this for some time now, as some have mentioned here, but we want to bring the spec in-line with Legion, so we’ve opted to not allow Shadowstrike to be merged with other abilities through the use of macros. The same goes for Shadow Dance, etc.

I would say that generally the use case of abilities while in/out of combat are very different, and with Rogues we do want to keep the use of the Stealth bar while out of combat to concrete that difference.

Then why did you merge shred/ravage and pounce/rake but not backstab/shadowstrike?

We could have gone that direction, but we chose not to. There are a couple of reasons here, but just to note: Druids have a ton of abilities, and there was little distinction between the abilities you mentioned in general. Feral Druids in particular also do not have any major emphasis on in-combat stealth, so you don't typically use both spells in those pairs intermixed.

Comparing that to Subtlety Rogues: Backstab and Shadowstrike are both used rotationally, and we opted to not let them be merged. We decided instead to differentiate them as much as possible (replacing Ambush with Shadowstrike), such as by adding the teleport on to Shadowstrike.

but it does beg the question, why is a community manager saying this to us and not a dev themself?

Devs are still here, reading feedback. We're just extremely swamped with polishing things up for the quickly-approaching release of Legion, so enlisted the aid of the CMs to post on our behalf (as they usually do for the majority of WoW's lifecycles anyway).